Re: PGSQL 9.3 - Materialized View - multithreading

On 4 April 2014 17:29, Nicolas Paris <niparisco@gmail.com> wrote:
> Hello,
>
> My question is about multiprocess and materialized View.
> http://www.postgresql.org/docs/9.3/static/sql-creatematerializedview.html
> I (will) have something like 3600 materialised views, and I would like to
> know the way to refresh them in a multithread way
> (anderstand 8 cpu cores -> 8 refresh process  in the same time)

The only thing that immediately comes to mind would be running a
rather hacky DO function in 4 separate sessions:

DO $$
DECLARE
  session CONSTANT BIGINT := 0;
  rec RECORD;
BEGIN
  FOR rec IN SELECT quote_ident(nspname) || '.' ||
quote_ident(relname) AS mv FROM pg_class c INNER JOIN pg_namespace n
ON c.relnamespace = n.oid WHERE relkind = 'm' AND c.oid::bigint % 8 =
session LOOP
    RAISE NOTICE 'Refreshing materialized view: %', rec.mv;
    EXECUTE 'REFRESH MATERIALIZED VIEW ' || rec.mv || ';';
  END LOOP;
END$$ language plpgsql;

Where you would set session to 0 for the first session, 1 for the
next, 2 for the next and 3 for the next, and so on until you reach 7
for the last.  These would each be run in a separate parallel session,
although someone may come up with a better solution.

--
Thom